Low swing signaling is an effective technique to reduce power consumption on interconnects (e.g., clock distribution networks, busses, etc.). FIG. 1 shows a generic view of a low swing voltage signaling scheme 100 for interconnects. Low swing voltage signaling scheme 100 comprises multiple repeaters (Repeater-1, Repeater-2, and Repeater-3) which drive the signal “Input” over multiple interconnects to generate signal “Output.”
At the transmitter end of interconnect line 102, a high-swing to low-swing driver 101 (Repeater-1) reduces the voltage range of Vcc-Hi to Vss-Hi to the low-swing voltage range of Vcc-Lo to Vss-Lo. High-swing to low-swing driver 101 consists of a first inverter having p-type transistor P1 coupled to n-type transistor N1, where P1 is coupled to Vcc-Hi and N1 is coupled to Vss-Hi. High-swing to low-swing driver 101 further consists of a second inverter having p-type transistor P2 coupled to n-type transistor N2, where P2 is coupled to Vcc-Lo and N2 is coupled to Vss-Lo. Vcc-Lo and Vss-Lo have power supply levels which are between Vcc-Hi and Vss-Hi power supply levels. At the receiver end, a level-restoration circuit (such as capacitive coupled boosting, charge pump based boosting, etc.) is used to minimize the static current consumption.
Repeater-2 and Repeater-3 are similar to Repeater-1, and each uses multi-supplies to operate this low swing signal transmission architecture. Repeater-2 consists of two inverters—the first inverter having transistors P3 and N3 and operating on Vcc-Hi and Vss-Hi supplies, while the second inverter consists of transistors P4 and N4 and operating on lower voltage range using Vcc-Lo and Vss-Lo. Repeater-3 consists of two inverters—the first inverter having transistors P5 and N5 and operating on Vcc-Hi and Vs s-Hi supplies, while the second inverter consists of transistors P6 and N6 and operating on lower voltage range using Vcc-Lo and Vss-Lo.
The static current consumption increases sharply if the difference between Vcc-Hi and Vcc-Lo or between Vss-Hi and Vss-Lo is higher than a threshold voltage (Vt). The voltage swing of signal on interconnect 102 is independent of the activity factor of input signal “Input.” Low voltage swing signaling scheme 100 requires two separate voltage supplies or second supply generation circuits (such as a charge pump or low-drop out regulators) to provide Vcc-Hi, Vcc-Lo, Vss-Hi, and Vss-Lo power supplies.